Open-label Safety Study in Adults With ADHD

To evaluate the long-term safety and tolerability of SEP 225289 in adult subjects with ADHD
by the incidence of adverse events (AEs; or serious AEs), AEs (or SAEs) leading to
discontinuation

Inclusion Criteria:

- Subject meets DSM 5 criteria for a primary diagnosis of ADHD (inattentive,
hyperactive, or combined presentation) established by a comprehensive psychiatric
evaluation that reviews DSM 5 criteria. Diagnosis is confirmed by CAADID Part 2 with
checklist for DSM 5.

- Subject has an ADHD RS IV with adult prompts score of ≥ 22 at screening and baseline.

- Subject has agreed to participate by providing written informed consent and is
willing and able to comply with the protocol, in the opinion of the investigator.

- Subject is 18 to 55 years old, inclusive, at the time of informed consent.

- Subject is male or a non-pregnant, non lactating female.

- Female subjects must have a negative serum pregnancy test; females who are post
menopausal (defined as at least 12 months of spontaneous amenorrhea) and those who
have undergone hysterectomy or bilateral oophorectomy will be exempted from the
pregnancy test.

- Female subjects of childbearing potential and male subjects with female partners of
childbearing potential must agree to use an effective and medically acceptable form
of birth control throughout the study period.

- Subject has a negative breath alcohol test and a negative urine drug screen (UDS) for
any illicit drug at screening.

- Subject is judged by the investigator to be suitable for participation in a 12 month
clinical trial involving open-label dasotraline treatment.

- Subject can read well enough to understand the informed consent form and other
subject materials.

Exclusion Criteria:

- Subject has a psychiatric disorder other than ADHD that has been the primary focus of
treatment at any time during the 12 months prior to screening.

- Subject has a past history of, or current presentation consistent with, bipolar
disorder (including bipolar I and bipolar II), schizophrenia, schizoaffective
disorder, or any other psychotic disorder, or a personality disorder per DSM 5
criteria.

- Subject has a history of substance abuse or drug dependence (excluding nicotine and
caffeine) within the 12 months prior to screening, as defined by the DSM 5 criteria.

- Subject has a history of epilepsy, seizures (except childhood febrile seizures),
unexplained syncope or other unexplained blackouts (except single incident), or head
trauma with loss of consciousness lasting more than 5 minutes.

- Subject has a currently active medical condition (other than ADHD) that, in the
opinion of the investigator, could interfere with the ability of the subject to
participate in the study.

- Subject is currently taking or has taken within the previous 6 months an
anticonvulsant medication (eg, phenytoin, carbamazepine, lamotrigine, valproic acid,
etc); antipsychotic medication; or lithium (any lithium preparation or formulation).

- Subject is currently taking an alpha 2 adrenergic receptor agonist (including
clonidine and guanfacine), or serotonin-norepinephrine reuptake inhibitor (SNRI; eg,
venlafaxine), or dopamine-norepinephrine reuptake inhibitor (DNRI; eg, bupropion), or
monoamine oxidase [MAO] inhibitor. Note: Subjects who discontinue these medications
and wash-out from them for a minimum of 7 days prior to the first dose of study drug
will be allowed to enroll in the study.

- Subject is currently undergoing Cognitive Behavioral Therapy (CBT).

- Subject has a Body Mass Index (BMI) less than 18 or greater than 35 kg/m2 (see
Appendix V).

- Subject answers "yes" to "Suicidal Ideation" item 4 (active suicidal ideation with
some intent to act, without specific plan) or item 5 (active suicidal ideation with
specific plan and intent) on the C SSRS assessment at screening (in the past month).
Subjects who answer "yes" to this question must be referred to the investigator for
follow up evaluation.

- Subject has attempted suicide within 1 year prior to the screening period.

- Subject has history of positive test for Hepatitis B surface antigen or Hepatitis C
antibody and has liver function test results at screening above the upper limit of
normal for the reference lab.

- Subject is known to have tested positive for human immunodeficiency virus (HIV).

- Subject has a clinically significant abnormality on screening evaluation including
physical examination, vital signs, ECG, or laboratory tests that the investigator
considers to be inappropriate to allow participation in the study.

- The subject's screening ECG shows a corrected QT interval using Fridericia's formula
(QTcF) of ≥ 450 msec for male subjects or ≥ 470 msec for female subjects. Eligibility
will be based on the core laboratory ECG interpretation report.

- The subject's screening serum chemistry results show an alanine aminotransferase
(ALT) or aspartate aminotransferase (AST) value ≥ 2 times the upper limit of normal
(ULN), or a blood urea nitrogen (BUN) value ≥ 1.5 times the ULN for the reference
laboratory.

- Subject is currently participating or has participated in a clinical trial within the
last 90 days or has participated in more than 2 clinical trials within the past year.
This includes studies using marketed compounds or devices.

- Subject has a history of allergic reaction or has a known or suspected sensitivity to
any substance that is contained in the study drug formulation.

- Subject has previously been randomized in a clinical trial of dasotraline.

- Subject is likely to be noncompliant in the investigator's opinion.

- Subject is an investigational site staff member or the relative of an investigational
site staff member.